Manually balanced calorimeters of the Dubosc type have been known for more than a century. The generally large sample size and costly precision construction has lead to alternate colorimeters, generally shifting to electronic photo detection with analog logarithmic conversion of optical transmission (intensity) into absorbance or to microcomputers providing algorithmic conversion into absorbance.
U.S. Pat. No. 1,961,913 teaches a calorimeter for measuring the color or intensity of light reflected from a piece of material. A resistor (rheostat) is associated with a comparison incandescent light and includes a color indicating dial. The resistor varies the light intensity of the comparison incandescent light until a galvanometer reads the same as an incandescent light illuminating the sample. It is not clear how the intensity may be measured and at other times the color is measured. The colorimeter is not a pyrometer where the color of the filament is matched to the sample color temperature. There is no teaching of reading absorbance.
U.S. Pat. No. 2,042,281 teaches a moving a source of light along a rail until a sample and a reference photoelectric cell generate equal current as indicated by a galvanometer. An intensity scale associated with the position of the source of light can be determined by the inverse square law. The calorimeter is large and requires precision mechanical components.
There remains a need for a low cost calorimeter with a minimum of precision electronic components or microcomputers or precision mechanical components.
There also remains a need for a portable and rugged calorimeter.